1. Technical Field
The present disclosure relates to a method of inoculating magnesium (Mg) on compacted graphite iron (CGI), and a cylinder block and a cylinder head manufactured by using the method.
2. Related Art
Typically, a vehicle engine includes a cylinder block and a cylinder head. The cylinder block fixes a piston, a connecting rod, and a crank shaft and the cylinder head controls the flow of air, fuel, and combustion gas.
The cylinder block and head are manufactured by cast iron, more particularly, high-hardened hypereutectic compacted graphite iron (CGI). Such CGI is produced by preparing a pearlite matrix, which provides hardness, and inoculating 0.01˜0.015 wt % of Mg on a hypereutectic composition that comprises 3.6˜3.8 wt % of carbon (C), 1.9˜2.1 wt % of silicon (Si), and the like, which facilitates vermiform graphite eruption.
CGI-based products are prepared by melting CGI cast iron of the above-described composition in a melting furnace; tapping the melted liquid to a ladle and simultaneously performing a primary inoculation with Mg; in the case where a high amount of Mg is detected through thermal analysis, discarding the liquid and performing the tapping and the primary inoculation again; and in the case where an additional amount of Mg is needed, performing a secondary inoculation with Mg wire, or measuring temperature and performing injection process into a mold.
However, in the conventional method of manufacturing a CGI product, an initial reaction of Mg proceeds rapidly in the primary Mg inoculating process, and the deviation of density of Mg becomes severe, so that the secondary inoculating process is required.
Also, since the conventional CGI cast iron is composed of a hypereutectic composition, high-temperature graphite eruption causes inferior liquidity, and the defect rate of casting contraction becomes high due to high-temperature injection.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.